Certbot - SSL: unknown protocol error

We are trying to install and use Certbot. We have installed it and we tried to install one certificate (for https://www.tuxx.cn/), but this gives the following error when using Mozilla Firefox: SSL_ERROR_RX_RECORD_TOO_LONG

Using Curl, we also get an error (but a different one): curl: (35) error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol

This is our Apache configuration:

irtualHost *:443>
  ServerName www.tuxx.cn
  DocumentRoot /var/www/current/httpdocs

    SSLEngine on

    # Intermediate configuration, tweak to your needs
    SSLProtocol             all -SSLv2 -SSLv3
    SSLCipherSuite          ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES12$
    SSLHonorCipherOrder     on
    SSLCompression          off

    SSLOptions +StrictRequire

    SSLCertificateFile /etc/letsencrypt/live/www.tuxx.cn/fullchain.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/www.tuxx.cn/privkey.pem
 <Directory "/var/www/current/httpdocs">
    AllowOverride All
    Options -Indexes +FollowSymLinks
    Require all granted
  </Directory>
</VirtualHost>

What are we doing wrong here?

P.S. We tried to find out what the difference was between the default certbot Apache configuration and our Apache configuration. It turned out that we had to split our configuration into subconfigurations per domain in order for certbot to detect the configuration files.